Silicon carbide epitaxial wafer preparation method and silicon carbide epitaxial growth equipment

Abstract

The present application provides a method for preparing a silicon carbide epitaxial wafer and a silicon carbide epitaxial growth device, the method comprising: placing a silicon carbide substrate on a tray; using a doping source gas path to transport a doping source gas to a gas source mixing area; using a growth source gas path to transport a growth source gas to a gas source mixing area; the doping source gas comprises R x NH y , x and y are natural numbers, x + y = 3, R represents a group or element, the temperature of the gas source mixing zone is not less than the threshold temperature, the threshold temperature indicates that there is no SiN z (z represents the ratio of Si to N) The minimum temperature required for parasitic growth; when the growth source gas and the doping source gas reach the gas source reaction zone, the growth source gas and the doping source gas are controlled to react to form a silicon carbide epitaxial wafer on the surface of the silicon carbide substrate away from the tray. This application solves the problems of uneven doping concentration and strong doping memory effect in n-type silicon carbide epitaxial layers in the prior art, resulting in poor device performance.

Description

Technical Field

[0001] The present application relates to the field of SiC epitaxial technology, and in particular to a method for preparing a silicon carbide epitaxial wafer, a silicon carbide epitaxial growth device, and a silicon carbide epitaxial wafer. Background Art

[0002] Silicon carbide, a wide-bandgap semiconductor material, boasts a range of advantageous properties, including a large bandgap, high breakdown electric field, high thermal conductivity, and fast saturation drift velocity. It holds broad application prospects in high-voltage, high-power, high-temperature, and high-frequency applications, potentially resolving bottlenecks in the development of silicon power semiconductor devices. The preparation of high-quality, lightly nitrogen-doped epilayers is crucial for designing the epitaxial layer structure and performance parameters required for high-voltage SiC power devices. Currently, nitrogen is the primary doping source used in industry. However, due to the very high triple bond energy between nitrogen atoms in nitrogen and the difficulty in controlling its thermal decomposition, achieving a uniform distribution of nitrogen partial pressure across the substrate surface is difficult. Furthermore, nitrogen doping efficiency is low, and some nitrogen is adsorbed by reactor chamber deposits, resulting in a strong memory effect and poor process reproducibility. Therefore, to achieve low background doping concentrations and further improve epitaxial layer doping uniformity, thereby reducing device performance variability and improving device reliability, selecting a more appropriate n-doping source and mastering its growth process are key challenges in silicon carbide epitaxy. Summary of the Invention

[0003] The main purpose of this application is to provide a method for preparing a silicon carbide epitaxial wafer, a silicon carbide epitaxial growth device and a silicon carbide epitaxial wafer, so as to solve the problems in the prior art of uneven doping concentration of the n-type silicon carbide epitaxial layer and strong doping memory effect leading to poor device performance.

[0004] In order to achieve the above object, according to one aspect of the present application, a method for preparing a silicon carbide epitaxial wafer is provided, comprising: placing a silicon carbide substrate on a tray; delivering a doping source gas to a gas source mixing area using a doping source gas path, and delivering a growth source gas to the gas source mixing area using a growth source gas path, wherein the doping source gas comprises R x NH y , x and y are both natural numbers, x+y=3, R represents a group or element, the growth source gas includes at least a carbon source and a silicon source, the temperature of the gas source mixing zone is not less than a threshold temperature, the threshold temperature represents the absence of SiN z(z represents the ratio between Si and N) the minimum temperature required for parasite generation; when the growth source gas and the doping source gas reach the gas source reaction zone, the growth source gas and the doping source gas are controlled to react to generate a silicon carbide epitaxial wafer on the surface of the silicon carbide substrate away from the tray, the temperature of the gas source reaction zone is not less than the growth temperature, and the growth temperature represents the minimum temperature required to generate the silicon carbide epitaxial wafer.

[0005] Optionally, after placing the silicon carbide substrate on the tray and before controlling the growth source gas to react with the doping source gas, the method further includes: controlling the tray to rotate by utilizing gas delivered to the bottom of the tray by a flotation gas line.

[0006] In order to achieve the above-mentioned purpose, according to one aspect of the present application, a silicon carbide epitaxial growth device is provided, and the silicon carbide epitaxial growth device is used for the preparation method of the silicon carbide epitaxial wafer. The silicon carbide epitaxial growth device comprises: an air inlet channel, comprising at least a doping source air path and a growth source air path, the doping source air path is used to convey the doping source gas, and the growth source air path is used to convey the growth source gas; a tray is used to place the silicon carbide substrate; a gas source mixing zone is provided at the outlet of the doping source air path and the outlet of the growth source air path, the doping source air path is used to convey the doping source gas to the gas source mixing zone, and the growth source air path is used to convey the growth source gas to the gas source mixing zone, and the temperature of the gas source mixing zone is not less than a threshold temperature, and the threshold temperature represents the absence of SiN z (z represents the ratio between Si and N) the minimum temperature required for parasite generation; a gas source reaction zone is arranged on a side of the silicon carbide substrate away from the tray, the temperature of the gas source reaction zone is not less than the growth temperature, and the growth temperature represents the minimum temperature required to generate the silicon carbide epitaxial wafer.

[0007] Optionally, the silicon carbide epitaxial growth equipment also includes: a first heating element, which is arranged on a side of the gas source reaction zone away from the tray, and the first heating element and the doping source gas path are arranged on the same side of the gas source reaction zone, and the first heating element is used to heat the gas source reaction zone so that the temperature of the gas source reaction zone is not lower than the growth temperature.

[0008] Optionally, the silicon carbide epitaxial growth equipment further includes: a second heating element, the tray is arranged on a portion of the surface of the second heating element close to the gas source reaction zone, and the second heating element is used to heat the tray.

[0009] Optionally, the outlet of the doping source gas path is arranged in the first heating element, the gas source mixing zone and the gas source reaction zone are located in the same area, and the temperature of the gas source mixing zone is not less than the growth temperature.

[0010] Optionally, the outlet of the doping source gas path is arranged on one side of the first heating element, and the gas source mixing zone and the gas source reaction zone are located in different areas.

[0011] Optionally, the silicon carbide epitaxial growth equipment also includes: a spray port, which is arranged on a portion of the surface of the first heating element close to the gas source reaction zone, the spray port includes a plurality of spaced gas outlets arranged along its axial direction, and the outlet of the doping source gas path is arranged in the spray port.

[0012] Optionally, the air inlet channel also includes: a flotation gas path, which is arranged on the side of the growth source gas path away from the doping source gas path, and the outlet of the flotation gas path is arranged in the second heating element, and the flotation gas path is used to transport gas to the bottom of the tray to make the tray rotate.

[0013] Optionally, the silicon carbide epitaxial growth equipment further includes: a first heat insulating member, disposed on a surface of the first heating member away from the gas source reaction zone.

[0014] Optionally, the silicon carbide epitaxial growth equipment further includes: a second heat insulating member, disposed on a surface of the second heating member away from the gas source reaction zone.

[0015] Optionally, the silicon carbide epitaxial growth equipment further includes a quartz cover, and the gas inlet channel, the tray, the gas source mixing zone and the gas source reaction zone are all arranged in the quartz cover.

[0016] According to another aspect of the present application, a silicon carbide epitaxial wafer is provided, wherein the silicon carbide epitaxial wafer is prepared using the method for preparing the silicon carbide epitaxial wafer.

[0017] In applying the technical solution of the present application, a silicon carbide substrate is first placed on a tray, and then a doping source gas is transported to a gas source mixing area using a doping source gas path, and a growth source gas is transported to a gas source mixing area using a growth source gas path. Finally, when the growth source gas and the doping source gas reach the gas source reaction area, the growth source gas is controlled to react with the doping source gas to form a silicon carbide epitaxial wafer on the surface of the silicon carbide substrate away from the tray, wherein the doping source gas includes R x NH y , the temperature of the gas source mixing zone is not less than the threshold temperature. Compared with the problems of uneven doping concentration and strong doping memory effect in the prior art n-type silicon carbide epitaxial layer leading to poor device performance, the present application selects R x NH yAs the n-doping source, due to its low thermal decomposition energy, it can greatly reduce the memory effect and improve the problem of uneven nitrogen partial pressure distribution on the wafer surface, thereby achieving the effect of improving the in-plane uniformity of n-doping in silicon carbide epitaxial wafers; In addition, the doping source gas and the growth source gas are transported separately, and the gas source mixing zone ensures that there is no SiN z The temperature range of parasite growth is within the range of NH4Cl solid products and high stability silicon nitrogen parasite SiN z The generation of , reduces the defect density of the prepared n-type epitaxial wafer, thereby ensuring better performance of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The drawings that constitute part of this application are used to provide a further understanding of this application. The illustrative embodiments of this application and their descriptions are used to explain this application and do not constitute an improper limitation on this application. In the drawings:

[0019] Figure 1 A schematic flow chart of a method for preparing a silicon carbide epitaxial wafer according to an embodiment of the present application is shown;

[0020] Figure 2 A schematic structural diagram of a silicon carbide epitaxial growth device provided according to an embodiment of the present application is shown;

[0021] Figure 3 A schematic structural diagram of another silicon carbide epitaxial growth device provided according to an embodiment of the present application is shown;

[0022] Figure 4 A schematic diagram of a partial structure of a silicon carbide epitaxial growth device provided according to an embodiment of the present application is shown;

[0023] Figure 5 A partial structural schematic diagram of another silicon carbide epitaxial growth device provided according to an embodiment of the present application is shown.

[0024] The above drawings include the following reference numerals:

[0025] 10. Air inlet channel; 11. Tray; 13. Gas source mixing zone; 101. Doping source gas path; 17. First outlet; 102. Growth source gas path; 14. Gas source reaction zone; 15. First heating element; 16. Second heating element; 18. Spray port; 181. Gas outlet; 103. Flotation gas path; 19. First thermal insulation element; 20. Second thermal insulation element; 21. Quartz cover. DETAILED DESCRIPTION

[0026] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present application belongs.

[0027] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0028] It should be understood that when an element (such as a layer, film, region, or substrate) is described as being “on” another element, the element may be directly on the other element or intervening elements may be present. Furthermore, in the specification and claims, when it is described that an element is “connected to” another element, the element may be “directly connected to” the other element or “connected to” the other element through a third element.

[0029] As introduced in the background technology, the doping concentration of the n-type silicon carbide epitaxial layer in the prior art is uneven. To solve the above problem, the embodiments of the present application provide a method for preparing a silicon carbide epitaxial wafer, a silicon carbide epitaxial growth device and a silicon carbide epitaxial wafer.

[0030] The technical solutions in the embodiments of the present invention will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present invention.

[0031] Figure 1 FIG is a flow chart of a method for preparing a silicon carbide epitaxial wafer according to an embodiment of the present application. Figure 1 As shown, the method includes the following steps:

[0032] Step S101, placing a silicon carbide substrate on a tray;

[0033] Step S102: Using the doping source gas path to deliver the doping source gas to the gas source mixing area, and using the growth source gas path to deliver the growth source gas to the above-mentioned gas source mixing area. The above-mentioned doping source gas includes R x NH y , x and y are both natural numbers, x+y=3, R represents a group or element, the above-mentioned growth source gas includes at least a carbon source and a silicon source, the temperature of the above-mentioned gas source mixing zone is not less than the threshold temperature, and the above-mentioned threshold temperature represents the absence of SiN z (z represents the ratio between Si and N) The minimum temperature required for parasite formation;

[0034] Step S103, when the above-mentioned growth source gas and the above-mentioned doping source gas reach the gas source reaction zone, the above-mentioned growth source gas and the above-mentioned doping source gas are controlled to react to generate a silicon carbide epitaxial wafer on the surface of the above-mentioned silicon carbide substrate away from the above-mentioned tray, and the temperature of the above-mentioned gas source reaction zone is not less than the growth temperature, and the above-mentioned growth temperature represents the minimum temperature required to generate the above-mentioned silicon carbide epitaxial wafer.

[0035] According to this embodiment, the silicon carbide substrate is first placed on the tray, and then the doping source gas is transported to the gas source mixing area by the doping source gas path, and the growth source gas is transported to the gas source mixing area by the growth source gas path. Finally, when the growth source gas and the doping source gas reach the gas source reaction area, the growth source gas and the doping source gas are controlled to react to form a silicon carbide epitaxial wafer on the surface of the silicon carbide substrate away from the tray, wherein the doping source gas includes R x NH y , the temperature of the gas source mixing zone is not less than the threshold temperature. Compared with the problems of uneven doping concentration and strong doping memory effect in the prior art n-type silicon carbide epitaxial layer leading to poor device performance, the present application selects R x NH y As the n-doping source, due to its low thermal decomposition energy, it can greatly reduce the memory effect and improve the problem of uneven nitrogen partial pressure distribution on the wafer surface, thereby achieving the effect of improving the in-plane uniformity of n-doping in silicon carbide epitaxial wafers; In addition, the doping source gas and the growth source gas are transported separately, and the gas source mixing zone ensures that there is no SiN z The temperature range of parasite growth is within the range of NH4Cl solid products and high stability silicon nitrogen parasite SiN z The generation of , reduces the defect density of the prepared n-type epitaxial wafer, thereby ensuring better performance of the device.

[0036] Specifically, R x NH y In the equation, R can be any substituent group such as CH3, C2H4, C2H5, C3H7, CO, C6H5, or any element such as Si, C, In. For example, when x=0 and y=3, R x NH y is NH3; when x=1, y=2, R is CH3, R x NH y is CH3NH2; when x=1, y=2, R is CO, R x NH y is CONH2; when x=2, y=1, R is C6H5, R x NH y is (C6H5)2NH; when x=3, y=0, R is C5H5, R xNH y is (C5H5)3N; when x=1, y=2, R is Si, R x NH y is SiNH2.

[0037] Specifically, SiN z It is an amorphous material whose properties depend on the ratio of Si to N, that is, the value of z.

[0038] Specifically, the threshold temperature is the temperature at which the thermodynamically stable phase is pure SiC. Pure SiC is different from silicon carbide epitaxial wafers (the ratio of Si to C and the crystal structure of the two are different).

[0039] It should be noted that, if you select R x NH y (x and y are both natural numbers, x+y=3, R represents a group or element) as n-doping sources, because such molecules contain doping atoms N but do not have high-energy nitrogen-nitrogen double bonds and nitrogen-nitrogen triple bonds, and are effective dopants for preparing high-quality n-type SiC epitaxial wafers. However, further research found that the following problems exist in the actual process: 1) Generation of NH4C1-type solid products: In response to the needs of SiC thick epitaxy, a chlorine-based rapid epitaxy method is usually used to grow n-doped epitaxial layers. At room temperature, chlorine-based gases mixed with ammonia or its hydrocarbon-based substituents will generate NH4C1-type solid products and adhere to the mass flow meter and process pipelines, causing blockage. The sublimation temperature of the NH4C1 solid product is 338°C, and the melting point of monomethylamine hydrochloride is 220-230°C. This means that in order to avoid this problem, it is at least necessary to ensure that the mixing temperature of this type of doping source and the growth source gas is greater than the decomposition temperature; 2) High stability SiN z Generation: Due to the high reactivity of ammonia or its hydrocarbon substituents, they will react with silicon compounds to form nitrogen-silicon compounds. These substances have excellent thermal stability and can remain stable in high temperature environments. This means that once these substances are generated, they cannot be decomposed and eliminated. Therefore, we need to eliminate the generation of such substances from the beginning. Since the content of ammonia or its hydrocarbon substituents as doping sources is generally less than 1 / 10 of the C source gas flow rate, based on the C / Si / N / H phase diagram obtained by thermodynamic calculations in reference literature, it can be seen that at this time, if the mixing temperature is greater than 800K, the thermodynamically stable product is pure SiC, without SiN z Impurities, which means that in order to avoid the occurrence of this problem, it is necessary to at least ensure that the mixing temperature of this type of doping source and growth source gas is higher than the temperature at which the thermodynamically stable phase is a nitrogen silicon compound, to ensure that the thermodynamically stable product at this time is pure SiC.

[0040] Specifically, the growth source gas also includes a chlorine-based gas. x NH y(x and y are both natural numbers, x+y=3, R represents a group or element) are delivered separately from the growth source gas (carbon source / silicon source / chlorine-based gas) and mixed with the growth source gas within the temperature range where the thermodynamically stable phase is unique and is SiC (i.e., the threshold temperature) to prepare high-quality n-type silicon carbide epitaxial wafers.

[0041] In the embodiment of the present application, the threshold temperature is 520°C, and the growth temperature is 1000°C-1650°C.

[0042] In one optional embodiment, after placing the silicon carbide substrate on the tray and before controlling the growth source gas to react with the doping source gas, the method further includes: controlling the tray to rotate using gas delivered to the bottom of the tray via the flotation gas line. In this embodiment, controlling the tray to rotate, thereby driving the rotation of the silicon carbide substrate, further ensures good n-doping uniformity in the resulting silicon carbide epitaxial wafer.

[0043] The present application also provides a silicon carbide epitaxial growth device, which is used in the above-mentioned method for preparing the silicon carbide epitaxial wafer. Figures 2 to 5 As shown, the above-mentioned silicon carbide epitaxial growth equipment includes:

[0044] The gas inlet channel 10 comprises at least a doping source gas path 101 and a growth source gas path 102. The doping source gas path 101 is used to transport the doping source gas, and the growth source gas path 102 is used to transport the growth source gas.

[0045] Tray 11, used for placing a silicon carbide substrate (not shown);

[0046] The gas source mixing zone 13 is provided at the outlet of the doping source gas path 101 (i.e., the first outlet 17) and the outlet of the growth source gas path 102. The doping source gas path 101 is used to deliver the doping source gas to the gas source mixing zone 13. The growth source gas path 102 is used to deliver the growth source gas to the gas source mixing zone 13. The temperature of the gas source mixing zone 13 is not less than the threshold temperature. The threshold temperature indicates that there is no SiN. z (z represents the ratio between Si and N) The minimum temperature required for parasite formation;

[0047] The gas source reaction zone 14 is disposed on a side of the silicon carbide substrate away from the tray 11 . The temperature of the gas source reaction zone 14 is not less than the growth temperature. The growth temperature represents the minimum temperature required to grow a silicon carbide epitaxial wafer.

[0048] Through the above embodiment, the silicon carbide epitaxial growth equipment includes an air inlet channel, a tray, a gas source mixing zone and a gas source reaction zone, wherein the air inlet channel includes at least a doping source gas path and a growth source gas path, the doping source gas path is used to transport the doping source gas to the gas source mixing zone, the growth source gas path is used to transport the growth source gas to the gas source mixing zone, and the temperature of the gas source mixing zone is not less than the threshold temperature. Compared with the problems of uneven doping concentration of n-type silicon carbide epitaxial layer and strong doping memory effect leading to poor device performance in the prior art, the present application transports the doping source gas and the growth source gas separately through the doping source gas path and the growth source gas path, and the gas source mixing zone ensures that the doping source gas and the growth source gas are not uniform in the absence of SiN. z The temperature range of parasite growth is within the range of NH4Cl solid products and high stability silicon nitrogen parasite SiN z The generation of defects can reduce the defect density of the prepared n-type silicon carbide epitaxial wafer, ensure the high quality of the silicon carbide epitaxial wafer, and thus ensure the better performance of the device.

[0049] In one option, Figures 2 to 5 As shown, the silicon carbide epitaxial growth apparatus further includes a first heating element 15 disposed on a side of the gas source reaction zone 14 away from the tray 11. The first heating element 15 and the dopant source gas line 101 are disposed on the same side of the gas source reaction zone 14. The first heating element 15 is configured to heat the gas source reaction zone 14 to maintain a temperature no less than the growth temperature. In this embodiment, the first heating element is configured to heat the gas source reaction zone, further ensuring good doping uniformity in the resulting n-type silicon carbide epitaxial wafer, thereby further ensuring high quality of the resulting silicon carbide epitaxial wafer.

[0050] In other embodiments, Figures 2 to 5 As shown, the silicon carbide epitaxial growth apparatus further includes a second heating element 16. The tray 11 is disposed on a portion of the second heating element 16 near the gas source reaction zone 14. The second heating element 16 is configured to heat the tray 11. In this embodiment, the second heating element heats the tray, thereby ensuring a high temperature at the bottom surface of the silicon carbide substrate and minimizing the temperature difference between the upper and lower surfaces of the silicon carbide substrate, further ensuring high quality of the resulting silicon carbide epitaxial wafer.

[0051] Specifically, the first heating element and the second heating element are both dense graphite elements, which are surrounded by coils. Alternating current is supplied to the coils, and electromagnetic induction is used for heating.

[0052] Some other options, such as Figure 2 、 Figure 4 and Figure 5As shown, the outlet of the dopant source gas circuit 101 (i.e., the first outlet 17) is located within the first heating element 15. The gas source mixing zone 13 and the gas source reaction zone 14 are located in the same area, and the temperature of the gas source mixing zone 13 is not less than the growth temperature. In this embodiment, the outlet of the dopant source gas circuit is located within the first heating element, ensuring a high outlet temperature of the dopant source gas circuit, thereby further ensuring that the dopant source gas and the growth source gas can react well to form silicon carbide epitaxial wafers, further avoiding the generation of NH4Cl-based solid products and highly stable nitrogen-silicon parasites SiN. z The generation of further ensures the high quality of the obtained silicon carbide epitaxial wafer.

[0053] Specifically, when the outlet of the doping source gas path is arranged in the first heating element, an anti-corrosion coating is provided around the outlet of the doping source gas path to avoid R x NH y (x and y are both natural numbers, x+y=3, R represents a group or element) The corrosion of the above-mentioned first heating element by the substance.

[0054] Specifically, Figure 4 (b) Figure 4 (a) Corresponding top view.

[0055] Among some other options, such as Figure 3 As shown, the outlet of the doping source gas path 101 is disposed on one side of the first heating element 15 , and the gas source mixing zone 13 and the gas source reaction zone 14 are located in different areas.

[0056] In some exemplary embodiments, Figure 5 As shown, the above-mentioned silicon carbide epitaxial growth equipment also includes: a spray port 18, which is arranged on a portion of the surface of the above-mentioned first heating element 15 close to the above-mentioned gas source reaction zone (not shown), and the above-mentioned spray port 18 includes a plurality of spaced gas outlets 181 arranged along its axial direction, and the outlet of the above-mentioned doping source gas path 101 (i.e., the first outlet 17) is arranged in the above-mentioned spray port 18.

[0057] Specifically, Figure 5 (b) Figure 5 (a) Corresponding top view.

[0058] Specifically, if Figure 5 As shown, the outlet of the doping source gas path 101 (ie, the first outlet 17 ) completely overlaps with the spray port 18 , and the diameter of the spray port 18 is w.

[0059] Specifically, a spray nozzle is provided on the bottom surface of the first heating element. The spray nozzle is circular, and the diameter w of the spray nozzle satisfies 0 < w < 1000 mm; preferably, 100 mm < w < 270 mm. The gas outlet is circular, the number of gas outlets is greater than or equal to 1, and the diameter of the gas outlet is greater than 0 and less than or equal to the diameter w of the spray nozzle.

[0060] Specifically, by providing the spray nozzle, the gas vortex near the outlet of the doping source gas path can be suppressed, achieving a good uniform gas mixing effect, and avoiding a large decrease in the temperature near the outlet of the doping source gas path, thereby further suppressing the formation of solid products such as NH4Cl and nitrogen-silicon parasites SiN in the gas source mixing region. z in the gas source mixing region.

[0061] In some other exemplary embodiments, as Figures 2 to 5 shown, the above-mentioned intake passage 10 further includes: an air flotation gas path 103, which is provided on the side of the growth source gas path 102 away from the doping source gas path 101. The outlet of the air flotation gas path 103 is provided inside the second heating element 16. The air flotation gas path 103 is used to transport gas to the bottom of the tray 11, so that the tray 11 rotates. In this embodiment, the air flotation gas path is used to transport gas to the bottom of the tray, so that the tray rotates, thereby driving the rotation of the silicon carbide substrate, and further ensuring better uniformity of n-doping of the obtained silicon carbide epitaxial wafer.

[0062] Specifically, in the present application, the silicon carbide epitaxial growth equipment includes a growth chamber, a tray, and an intake pipe. The intake pipe has a doping source gas path, a growth source gas path, and an air flotation gas path. The doping source gas path is used to introduce a doping source gas R x NH y (both x and y are natural numbers, x + y = ३, and R represents a group or an element). The growth source gas path is used to introduce C-based gases (such as gases containing C atoms like propane, ethylene, methyltrichlorosilane, and methane), Si-based gases (such as gases containing Si atoms like silane, trichlorosilane, and methyltrichlorosilane), and other gases (such as hydrogen, hydrogen chloride, and argon) required for SiC epitaxial growth. The three types of gas path pipes are separated from each other, but each gas path pipe does not necessarily have to be a single pipe and can have multiple gas path pipes.

[0063] In some further exemplary embodiments, as Figures 2 to 5 shown, the above-mentioned silicon carbide epitaxial growth equipment further includes: a first heat insulator 19, which is provided on the surface of the first heating element 15 away from the gas source reaction zone 14. In this embodiment, the first heat insulator ensures that less heat generated by the first heating element is dissipated to the outside.

[0064] In other embodiments, as Figures 2 to 5As shown, the silicon carbide epitaxial growth apparatus further includes a second heat insulating member 20 disposed on a surface of the second heating member 16 away from the gas source reaction zone 14. In this embodiment, the second heat insulating member ensures that less heat generated by the second heating member is dissipated to the outside.

[0065] Specifically, the first thermal insulation member and the second thermal insulation member are made of thermal insulation graphite, which has very low thermal conductivity.

[0066] In other embodiments, Figure 2 and Figure 3 As shown, the silicon carbide epitaxial growth device further includes a quartz cover 21 , in which the gas inlet channel 10 , the tray 11 , the gas source mixing zone 13 and the gas source reaction zone 14 are all disposed.

[0067] The following will describe the method for preparing the silicon carbide epitaxial wafer of the present application in detail with reference to specific examples and comparative examples. Example 1 and Example 2 are examples of preparing silicon carbide epitaxial wafers using the method for preparing the silicon carbide epitaxial wafer of the present application.

[0068] Example 1

[0069] The silicon carbide epitaxial growth apparatus described in this application was used as a SiC chemical vapor deposition apparatus. Trichlorosilane and ethylene were used as the SiC epitaxial wafer growth source gases, introduced through the growth source gas line. Ammonia was selected as the n-doping source and introduced through the doping source gas line. The growth temperature was set to 1500°C, the pressure to 100 mbar, and the ammonia flow rate to 0.5 sccm. SiC epitaxial layers were grown on the SiC substrate surface.

[0070] Comparative Example 1

[0071] A conventional horizontal SiC chemical vapor deposition (CVD) system was used as the SiC CVD equipment. Trichlorosilane and ethylene were used as the source gases for SiC epitaxial wafer growth, introduced through the growth source gas line. Ammonia was also selected as the n-doping source and introduced through the growth source gas line to mix directly with the growth source gas. The growth temperature was set to 1500°C, the pressure to 100 mbar, and the ammonia flow rate to 0.5 sccm. SiC epitaxial wafers were grown on the SiC substrate surface. White particles of ammonium chloride were observed on the walls of the ventilation duct (i.e., the walls of the growth source gas line), along with the formation of nitrogen-silicon parasites.

[0072] Comparative Example 2

[0073] The silicon carbide epitaxial growth equipment of the present application is used as SiC chemical vapor deposition equipment. Trichlorosilane and ethylene are used as the growth source gases for the SiC epitaxial wafer, which are introduced from the growth source gas line. Nitrogen is selected as the n-doping source and introduced from the doping source gas line. The growth temperature is set to 1500°C, the pressure is set to 100mbar, the nitrogen flow rate is 80sccm, and the SiC epitaxial wafer is grown on the surface of the SiC substrate. At this time, due to the difficulty in controlling the thermal decomposition of nitrogen, the distribution of nitrogen partial pressure on the surface of the substrate is uneven, and the in-plane uniformity of the surface doping concentration of the grown SiC epitaxial wafer is poor.

[0074] Example 2

[0075] The silicon carbide epitaxial growth equipment of the present application is used as SiC chemical vapor deposition equipment. Trichlorosilane and ethylene are used as the growth source gas for SiC epitaxial wafers, which are introduced from the growth source gas path. Ammonia is selected as the n-doping source and introduced from the doping source gas path. The gas is passed from the outlet of the doping source gas path into the gas source mixing zone to mix with the growth source gas. In addition, in order to solve the problems caused by uneven distribution of the doping source and nonlinear depletion, a small amount of ammonia can be appropriately added to the flotation gas path. At this time, the growth temperature is set to 1500°C, the pressure is 100mbar, the ammonia flow rate is 0.5sccm, and the SiC epitaxial wafer is grown on the surface of the SiC substrate.

[0076] In summary, in view of the problem that the nitrogen partial pressure distribution on the wafer surface is uneven due to the strong memory effect and difficult to control thermal decomposition of nitrogen gas, the present application selects R x NH y (x and y are both natural numbers, x+y=3, R represents a group or element) as the n-doping source gas, due to its low thermal decomposition energy, it can greatly reduce the memory effect and improve the problem of uneven distribution of nitrogen partial pressure on the wafer surface, thereby achieving the effect of improving the in-plane uniformity of n-doping of SiC epitaxial wafers. The effect of this invention can be illustrated by comparing the above embodiment 1 with the comparative example 2. x NH y (x and y are both natural numbers, x+y=3, R represents a group or element) as n-doping source gas to manufacture silicon carbide epitaxial wafers, there are NH4Cl-type solid products and highly stable nitrogen silicon parasites SiN zThe generation of nitrogen-free silicon parasites, combined with the previous analysis, shows that the temperature for the generation of nitrogen-free silicon parasites is higher than the decomposition temperature of NH4Cl-type solid products. Therefore, as long as the mixing temperature of the doping source gas and the growth source gas is at the temperature at which the nitrogen-free silicon parasites grow, the above two problems can be solved at the same time. Therefore, the present invention sets a separate doping source gas path so that its outlet, that is, the mixing temperature of the two types of source gases (that is, the temperature of the gas source mixing zone), ensures that the thermodynamically stable phase is unique and is SiC (that is, the temperature is not less than the threshold temperature), thereby avoiding the generation of NH4Cl-type solid products and highly stable nitrogen silicon parasites SiN z The purpose of preparing n-type silicon carbide epitaxial wafers with low defect density and high doping uniformity is finally achieved. The effect of this invention can be illustrated by comparing the above embodiment 1 with comparative example 1.

[0077] An embodiment of the present application further provides a silicon carbide epitaxial wafer, which is prepared using the above-mentioned method for preparing a silicon carbide epitaxial wafer.

[0078] In the above embodiment, the silicon carbide epitaxial wafer is prepared by using a method for preparing a silicon carbide epitaxial wafer, wherein, in the method for preparing the silicon carbide epitaxial wafer, the silicon carbide substrate is first placed on a tray, and then the doping source gas is transported to the gas source mixing area by using a doping source gas path, and the growth source gas is transported to the gas source mixing area by using a growth source gas path, and finally, when the growth source gas and the doping source gas reach the gas source reaction area, the growth source gas is controlled to react with the doping source gas to form a silicon carbide epitaxial wafer on the surface of the silicon carbide substrate away from the tray, wherein the doping source gas includes R x NH y , the temperature of the gas source mixing zone is not less than the threshold temperature. Compared with the problems of uneven doping concentration and strong doping memory effect in the prior art n-type silicon carbide epitaxial layer leading to poor device performance, the present application selects R x NH y As the n-doping source, due to its low thermal decomposition energy, it can greatly reduce the memory effect and improve the problem of uneven nitrogen partial pressure distribution on the wafer surface, thereby achieving the effect of improving the in-plane uniformity of n-doping in silicon carbide epitaxial wafers; In addition, the doping source gas and the growth source gas are transported separately, and the gas source mixing zone ensures that there is no SiN z The temperature range of parasite growth is within the range of NH4Cl solid products and high stability silicon nitrogen parasite SiN z The generation of , reduces the defect density of the prepared n-type epitaxial wafer, thereby ensuring better performance of the device.

[0079] From the above description, it can be seen that the above embodiments of the present application achieve the following technical effects:

[0080] In the method for preparing a silicon carbide epitaxial wafer of the present application, a silicon carbide substrate is first placed on a tray, and then a doping source gas is transported to a gas source mixing area using a doping source gas path, and a growth source gas is transported to a gas source mixing area using a growth source gas path, and finally, when the growth source gas and the doping source gas reach a gas source reaction area, the growth source gas is controlled to react with the doping source gas to form a silicon carbide epitaxial wafer on a surface of the silicon carbide substrate away from the tray, wherein the doping source gas includes R x NH y , the temperature of the gas source mixing zone is not less than the threshold temperature. Compared with the problems of uneven doping concentration and strong doping memory effect in the prior art n-type silicon carbide epitaxial layer leading to poor device performance, the present application selects R x NH y As the n-doping source, due to its low thermal decomposition energy, it can greatly reduce the memory effect and improve the problem of uneven nitrogen partial pressure distribution on the wafer surface, thereby achieving the effect of improving the in-plane uniformity of n-doping in silicon carbide epitaxial wafers; In addition, the doping source gas and the growth source gas are transported separately, and the gas source mixing zone ensures that there is no SiN z The temperature range of parasite growth is within the range of NH4Cl solid products and high stability silicon nitrogen parasite SiN z The generation of , reduces the defect density of the prepared n-type epitaxial wafer, thereby ensuring better performance of the device.

[0081] The above description is merely a preferred embodiment of the present application and is not intended to limit the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A method for preparing a silicon carbide epitaxial wafer, characterized in that: The silicon carbide epitaxial growth device is used in the method for preparing the silicon carbide epitaxial wafer. The silicon carbide epitaxial growth device includes: an air inlet channel, including at least a doping source air path and a growth source air path, the doping source air path is used to transport the doping source gas, and the growth source air path is used to transport the growth source gas; a tray; a gas source mixing zone, arranged at the outlet of the doping source air path and the outlet of the growth source air path, the doping source air path is used to transport the doping source gas to the gas source mixing zone, and the growth source air path is used to transport the growth source gas to the gas source mixing zone, the temperature of the gas source mixing zone is not less than a threshold temperature, and the threshold temperature represents the absence of SiN z The minimum temperature required for parasite formation, z represents SiN z The ratio of Si to N in the silicon carbide substrate is determined; a gas source reaction zone is provided on a side of the silicon carbide substrate away from the tray, the temperature of the gas source reaction zone is not less than a growth temperature, the growth temperature represents the minimum temperature required to grow a silicon carbide epitaxial wafer, the gas source mixing zone and the gas source reaction zone are located in different areas, the method comprising: placing a silicon carbide substrate on the tray; The doping source gas is transported to the gas source mixing area by using the doping source gas path, and the growth source gas is transported to the gas source mixing area by using the growth source gas path. The doping source gas includes R x NH y , x and y are both natural numbers, x+y=3, R represents a group or an element, and the growth source gas includes at least a carbon source and a silicon source; When the growth source gas and the doping source gas reach the gas source reaction zone, the growth source gas and the doping source gas are controlled to react with each other to form a silicon carbide epitaxial wafer on a surface of the silicon carbide substrate away from the tray.

2. The method for preparing a silicon carbide epitaxial wafer according to claim 1, wherein: The air inlet channel also includes: a flotation gas path, which is arranged on a side of the growth source gas path away from the doping source gas path, and the flotation gas path is used to transport gas to the bottom of the tray to rotate the tray. After placing the silicon carbide substrate on the tray, before controlling the growth source gas and the doping source gas to react, the method also includes: using the gas transported to the bottom of the tray by the flotation gas path to control the rotation of the tray.

3. The method for preparing a silicon carbide epitaxial wafer according to claim 1, wherein: The silicon carbide epitaxial growth equipment further comprises: A first heating element is arranged on a side of the gas source reaction zone away from the tray, and the first heating element and the doping source gas path are arranged on the same side of the gas source reaction zone. The first heating element is used to heat the gas source reaction zone so that the temperature of the gas source reaction zone is not less than the growth temperature.

4. The method for preparing a silicon carbide epitaxial wafer according to claim 2, wherein: The silicon carbide epitaxial growth equipment further comprises: The second heating element is used to heat the tray. The tray is arranged on a portion of the surface of the second heating element close to the gas source reaction zone.

5. The method for preparing a silicon carbide epitaxial wafer according to claim 3, wherein: The outlet of the doping source gas path is arranged on one side of the first heating element.

6. The method for preparing a silicon carbide epitaxial wafer according to claim 3, wherein: The silicon carbide epitaxial growth equipment further comprises: A spray port is provided on a portion of the surface of the first heating element close to the gas source reaction zone. The spray port includes a plurality of spaced gas outlets arranged along its axial direction. The outlet of the doping source gas path is provided in the spray port.

7. The method for preparing a silicon carbide epitaxial wafer according to claim 4, wherein: The outlet of the air flotation path is arranged in the second heating element.

8. The method for preparing a silicon carbide epitaxial wafer according to claim 3, wherein: The silicon carbide epitaxial growth equipment further comprises: The first heat insulating member is arranged on a surface of the first heating member away from the gas source reaction zone.

9. The method for preparing a silicon carbide epitaxial wafer according to claim 4, wherein: The silicon carbide epitaxial growth equipment further comprises: The second heat insulating member is arranged on a surface of the second heating member away from the gas source reaction zone.

10. The method for preparing a silicon carbide epitaxial wafer according to claim 1, wherein: The silicon carbide epitaxial growth equipment further comprises: A quartz cover, wherein the gas inlet channel, the tray, the gas source mixing zone and the gas source reaction zone are all arranged in the quartz cover.

11. A silicon carbide epitaxial wafer, characterized in that: The silicon carbide epitaxial wafer is prepared by the method for preparing the silicon carbide epitaxial wafer according to claim 1.

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